span.checkbox_check {
    cursor:pointer;
    background : url('checkbox/check.gif') no-repeat center;
    overflow: auto;
    height: 16px;
    width: 16px;
    padding-left: 11px;
  }


span.checkbox_uncheck {
    cursor:pointer;
    background : url('checkbox/uncheck.gif') no-repeat center;
    overflow: auto;
    height: 16px;
    width: 16px;
    padding-left: 11px;
  }

span.checkbox,
span.checkbox_undefined {
    cursor:pointer;
    background : url('checkbox/undefined.gif') no-repeat center;
    overflow: auto;
    height: 16px;
    width: 16px;
    padding-left: 11px;
  }